Thermocompressor



June 5 1951` J. F. PLUMMER, JR 2,555,812

Tax-:RuocouPaEssoR Filed Feb. 19, 1948 Hl 5 ATTORNEY,

Patented June 5, 1951 UNITED STATES, PATENT orties.N

THERMOCOMPRESSOR John F. Plummer, J r., Phillipsburg, N. J., assignor toIngersoll-'Rand Company, New York, N. Y., a

2 Claims.

l Ihisinvention relates to thermo-compressors ofthe steam ejector typewhich are capable of producing high vacuum pressures.

Ejectors of the type to which this invention appertains are normallyused in the rst stages of a thermo-compressor comprising a plurality ofsteam ejectors which are connected in series, i. e. with one ejectordischarging into the succeeding ejector, in order to produce a highvacuum. With this arrangement, the first and perhaps the second stageejector will be operating below the pressure at which water freezes,that is', at or below 4.5 mm.mercury and, therefore, the nozzles ofthese ejectors are constantly subjected to icing conditions. It isapparent then that any mois- 'ti'represent in the propelling steam maycondense and freeze in or on thenozzle and thereby impairitseliioientoperationz Y Experience has taught that this undesirableicingharacteristic may be eliminated b y superlocating the steam beforeit expands through the nozzle. Under normal circumstances, however, asufficient amount of vsuperheat is not available in the steam header toprovide a desired amount of superheat at the nozzle due to the radiantheat loss of the steam in passing from the header to the nozzle. Thatis, in the rst few stages of the thermo-compressor, only a very smallweight of propelling steam is necessary to move a large volume of thefluid to be evacuated because of the low pressures to which such fluidis exposed. As a result of this low rate of steam flow, say for examplefive pounds per hour for the first stage, the per unit, i. e. B. t.u./1b., radiation loss of the steam in passing between the header andthe nozzle may become excessive and the steam, though superheated in theheader, becomes wet before or upon reaching the nozzle.

The practice has, therefore, been to superheat the steam by an auxiliaryor external source of heat at some point near the nozzle therebypreventing icing of the nozzle. Another practice has been to allow thewet steam to expand through the nozzle and in some manner, as forexample by an electric heater, heat the nozzle to prevent the formationof ice on its surfaces. These two methods, however, require an auxiliarysource of power or heat.

The present invention is to reduce the per-unit heat loss of the steampassing from the header to the nozzle, to such a value that sufficientsuperheat is retained by the steam to prevent icing of the nozzle. Sincethe radiation loss of this steam is relatively constant for a givensteam temperature, the per-unit heat loss is inversely proporcorporationof New Jersey Application February 19, 1948, Seriai No. 9,400

tional to the flow rate of the steam and, therefore, the per-unit heatloss of such steam may be reduced to the aforesaid Value by controllingits flow rate.

It is accordingly one object of my invention to prevent icing of thenozzle of a steam ejector by reducing the per-unit heat loss of thesteam being delivered to the nozzle of a steam ejector.

Another object of my invention is 'to supply steam to the nozzle of afirst stage ejector of an ejector series7 in excess of that required tooperate said ejector and use such excess to operate the succeedingejector.

Other objects will be in part obvious and in part pointed outhereinafter.

The drawing accompanying this application,`- in which similar referencenumerals refer to similar parts, shows a side View in elevation, partlyin section, of a pair of series connected steam ejectors embodying thepresent invention.

Referring to the drawing, IB and Il indicate, respectively, the firsttwo stages of a `thermocompressorthe nrst stage ejector I0 of which isadapted to operate at or below the freezing pressure of water. Infurtherance of this end, the ejector Il) is provided with a non-icingnozzle unit I2 mounted on the ejector casing I3 adjacent the inlet I4for the fluid to be evacuated. Connected between a steam source (notshown) and the outer end of the nozzle unit I2 is a conduit I5 which isdesigned to convey energizing fluid or steam to the nozzle unit I2 inexcess of that discharged into the casing I3 by the unit I2. Such excessis conveyed from the nozzle unit I2 to the second stage ejector to actas the propelling fluid therefor.

In the form of the invention shown, the nozzle unit I2 comprises anozzle housing I6 having an orifice I'I at the inner end thereof forintroducing propelling steam into the mixing chamber I8 of the ejector,wherein the propelling fluid and the fluid to be evacuated are mixed andcarried into the diffuser IS. Adapted to bear on the opposite end of thehousingl is an abutting member 20 which forms an extension for thehousing I6 and has an opening 2| therein, whereby a portion of the steamsupplied to the nozzle housing is allowed to escape to a point externalof the ejector Il).

The abutting member 20 is aligned and held in form relation with thenozzle housing I G` by an internally threaded Washer 22 which bears on asealing ring 23 on the outer end 0f the housing I6 and is clampedthereto by any suitable means, such as the bolts 24.

.the ejector nozzles. vides `a simple and inexpensive means for pre- 3In order to minimize the per-unit heat loss of the steam delivered tothe orifice I1, means are provided within the nozzle unit I2 and spacedtherefrom for conveying steam to a point adjacent the orice Il, therebyreducing to a minimum the distance traveled by the propelling steammoving at a low rate of ilow. In this instance, such means is a tube 25that forms an extension for the conduit I5 and passes through theabutting member 2B and into the housing I6 to a point adjacent the oriceI'I. The lower end of the tube 25 is closed and in the side wall of thetube adjacent the end are perforations 26 to permit steam to escape intothe space between the tube 25 and the inner surface of the nozzlehousing. wherefrom a portion of the steam is discharged into the ejectorcasing I3 and the excess thereof escapes through the opening 2i into aconduit 2'1 connected to the nozzle 28 of the succeeding ejector I I.

In; the arrangement shown, a three-way valve mechanism 2S is connectedin thev conduits l5 and 21 to provide selective operation of theejectors I 0 and I I.l To this end the valve element 3U of .the valvemechanism has two passages 3i whereby the conduits 21 and i5 may becommuwith the power supply through one of the passages 3 I. Rotation ofthe element 3B through an -arcof forty-live degrees in either directionfrom either of the above mentioned positions will eiectively cut-off thepower source of both ej ectors.

- Itis now obvious to those. skilled in the art that the presentinvention permits the eiiicient operation of steam ejectors designed todevelope high vacuums without the additional expense of auxiliary orvexternal heatsource to prevent icing of The present inventionproper-unit heat loss of the energizing fluid-delivered to the ejectornozzle.

While I have shown and described one form of my invention it is to beunderstood that various changes and modifications may be made thereinwithout departing from the spirit of the invention as set forth in theappended claims.

I claim:

1. In a thermo-compressor, a plurality of steam ejectors connected inseries, nozzles for the ejectors, a tube extending into the nozzle ofthe rst stage ejector and terminating in a plane adjacent the downstreamend of said nozzle for supplying steam thereto in excess of thatrequired for operation of the first stage ejector, an opening in thefirst stage nozzle, and a conduit connected between the said opening andthe nozzle of the succeeding ejector for conveying said excess steamthereto.

2. In a thermo-compressor, a first stage ejector lconnected in. serieswith a second stage steam ejector, nozzles for the ejectors, a tubeextending into the nozzle for the rst stagel ejector and having a closedend lying in the transverse plane of said nozzle adjacent the downstreamend thereof, holes through the sides of the closedend portion of saidtube for communicating saidtube JOHN F. PLUMMER, JR..

REFERENCES CITED The following references are of record inthe ille ofthis patent:

UNITED STATES PATENTS Number Name Date 11,810,873. Sims .Jl1ne 16,19311,819,366; Lorraine Sept. 27, .1932 Ross Feb. 11, 1941

